Adipose Tissue Blood Flow Research Articles

Lactate release from the subcutaneous tissue in lean and obese men.

Lactate concentration in the subcutaneous interstitial fluid and adipose tissue blood flow (ATBF, ml/100 g.min) were simultaneously measured with the microdialysis technique combined with 133Xe clearance in the abdominal and femoral subcutaneous adipose tissue in nine lean and nine obese men. The studies were performed both in the postabsorptive state and 2 h after an oral glucose load and the results compared to the lactate levels in arterialized venous plasma. After an overnight's fast, arterial lactate was 738 +/- 49 and 894 +/- 69 microM (mean +/- SE) (P < 0.05) in the lean and obese subjects, respectively. The interstitial lactate levels were significantly higher than blood lactate in both subject groups without any regional differences. Abdominal and femoral ATBF was 3.2 +/- 0.6 vs. 2.8 +/- 0.4 and 1.7 +/- 0.3 vs. 2.4 +/- 0.4 ml/100 g.min (P < 0.05) in lean and obese subjects, respectively. Mean apparent lactate release from the abdominal vs. femoral adipose tissue in the fasting state was 10.5 +/- 3.1 vs. 8.6 +/- 2.3 and 6.0 +/- 2.3 vs. 8.5 +/- 2.3 mumol/kg.min (NS) in lean and obese subjects, respectively. Both plasma and interstitial lactate levels increased significantly after an oral glucose load in both subject groups. However, apparent lactate release increased significantly only in the lean group. It is concluded that subcutaneous adipose tissue is a significant source of whole-body lactate release in the postabsorptive state and that this is further enhanced in obese subjects due to their large adipose mass.

Lipolysis during abdominal surgery.

Subcutaneous adipose tissue lipolysis has been monitored with microdialysis during elective cholecystectomy by laparotomy in otherwise healthy nonobese subjects. Eight of the subjects received saline and seven received glucose iv during the operation. In both groups the glycerol level in the microdialysate (lipolysis index) started to increase steadily from the start of the general anesthesia until the abdominal wall was closed. Thereafter it leveled off and remained elevated until after extubation. Plasma glycerol started to rise after the surgical incision. The levels of noradrenaline and adrenaline, but not of insulin, glucagon, and cortisol in plasma, changed in parallel with that of glycerol in the microdialysate. The glycerol response in adipose tissue in the group receiving iv glucose was three times more marked than in the saline group (P = 0.01) in spite of marked hyperinsulinemia, but there was no difference between the groups in plasma glycerol response. The plasma noradrenaline response was 50% higher (P = 0.03) in the glucose group than in the saline group, but there was no difference between the groups in the plasma adrenaline, glucagon, or cortisol responses. Adipose tissue blood flow was measured by the escape of ethanol from the dialysis solvent into the extracellular space. It was constant throughout the experimental period in both groups. In conclusion, the lipolysis rate is accelerated during general anesthesia and abdominal surgery because of increased catecholamine production. Perioperative glucose infusion is associated with a further acceleration of the lipolytic rate in subcutaneous adipose tissue due to an additional activation of the sympathetic nervous activity that overrides the antilipolytic effect of the glucose-induced hyperinsulinemia. Other adipose regions may be less sensitive to glucose infusions and anesthesia.

Effect of phosphodiesterase inhibition with amrinone or theophylline on lipolysis and blood flow in human adipose tissue in vivo as measured with microdialysis

Phosphodiesterase III (cyclic GMP-inhibited, particulate, low Km) is believed to play a dominant role in the cyclic AMP breakdown and lipolysis regulation in fat cells. Its importance for lipolysis activity was investigated in situ in humans by comparing the effects of a selective (amrinone) and a nonselective (theophylline) inhibitor of the enzyme. Abdominal subcutaneous adipose tissue of healthy nonobese humans was microdialyzed with solvents containing one or both of these agents, and glycerol (lipolysis index) or the escape of ethanol from the dialysis solvent (blood flow index) was continuously monitored in the perfusate. Both agents caused a dose-dependent and sustained increase in the glycerol level in the perfusate for at least 2.5 h. Although amrinone was 5000 times more potent than theophylline on a molar basis, its maximum activity was only 35% as compared to the maximum activity of theophylline. Half-maximum lipolytic effect of the two drugs occurred at about 0.1 mumol/l and 1 mmol/l, respectively (P < 0.001). At maximum effective concentrations, amrinone stimulated lipolysis by about 63% and theophylline by about 200% (P < 0.01). At these concentrations amrinone increased the rate of disappearance of ethanol from the perfusate by about 20% and theophylline increased the rate by about 75%, the difference being statistically significant (P < 0.01). When the two drugs were added together, the level of lipolysis stimulation was not different from that with theophylline alone both at maximal and submaximal effective concentrations of drug combinations.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinically important differences in insulin absorption from abdomen in IDDM

The absorption of radiolabeled soluble insulin ([ 125I]Actrapid ® Human; 10 U) from subcutaneous injection sites above (120 mm) and below (40 mm) the umbilicus was studied on 2 consecutive days in nine IDDM patients during 180 min. Insulin absorption was measured as disappearance of radioactivity by continuous external monitoring and as appearance of plasma immunoreactive free insulin (IRI). Adipose tissue blood flow (ATBF) was measured concomitantly by the 133Xe-washout technique. Plasma glucose was determined. Prior to the injections the depth of the subcutaneous fat tissue was determined using ultrasound. Significantly less radioactivity remained at the upper site, 42 ± 5 vs. 60 ± 6% after 180 min ( P<0.001). In accordance with this, injection into the site above vs. below the umbilicus resulted in a greater area under curve for plasma insulin, 3306 ± 493 vs. 2357 ± 466 mU/l per min (0–180 min; P < 0.01), and a more pronounced plasma glucose-lowering effect ( P < 0.05). However, ATBF did not differ significantly between the two sites. These data suggest that there are clinically relevant differences in insulin absorption within the abdomen. Thus, insulin injection into the epigastric area causes more rapid insulin absorption resulting in an enhanced plasma glucose-lowering effect than injection into the more conventional site close beneath the umbilicus.

Intrascapular brown adipose tissue (IBAT) temperature and blood flow responses following ventromedial hypothalamic stimulation to sham and IBAT-denervated rats

Intrascapular brown adipose tissue temperature ( T IBAT) and capillary blood flow along with colonic ( T c ) and tail ( T t ) temperatures as well as blood pressure and heart rate responses were measured simultaneously in groups of age-natched, anesthetised, sham control and IBAT-denervated Long-Evans rats following VNH electrical stimulation. Unilateral VMH electrical stimulation (0.5 ms pulses of 100 μA at 50 Hz for 30 s) evoked rises in T IBAT (above core) and IBAT blood flow in the Long-Evans sham control group, along with increases in blood pressure and heart rate. Rises in IBAT temperature and capillary blood flow were absent in the surgical denervated group following VMH electrical stimulation whereas the evoked pressor and tachycardic responses were left intact and were similar to those responses seen in the sham control group. The results indicate that acute bilateral sectioning of the IBAT intercostal nerves blocks the IBAT temperature and capillary blood flow increases evoked by VMH electrical stimulation.

Periprandial regulation of lipid metabolism in insulin-treated diabetes mellitus

We have examined the regulation of lipid and glucose metabolism in the postabsorptive and postprandial states in six subjects with insulin-treated diabetes mellitus, and compared them with eight nondiabetic subjects. Blood or plasma concentrations of metabolites and fluxes across forearm and subcutaneous adipose tissue were studied after an overnight fast and for 6 hours after a mixed meal (3.1 MJ, 41% from fat). In the postabsorptive state, regulation of lipid metabolism in the two groups appeared basically similar except that a wider spread of plasma (free) insulin concentrations in the diabetic group led to a wider range of values of plasma nonesterified fatty acid (NEFA) release from adipose tissue, plasma NEFA concentrations, and blood ketone body concentrations. Extraction of ketone bodies across adipose tissue was positively correlated with arterial concentration in both groups (as it was in the forearm), confirming the ability of human adipose tissue to utilize ketone bodies. A single subcutaneous injection of insulin before the meal in the diabetic group produced a plasma free-insulin profile that was blunted and prolonged compared with the postprandial response in the control group. Postprandial forearm glucose uptake followed very closely the plasma (free) insulin concentration. Postprandial suppression of NEFA release from adipose tissue was essentially normal in the diabetic group, and the normal postprandial decrease in plasma NEFA concentrations was reproduced extremely closely. Forearm and adipose tissue blood flow did not differ between the groups. The results show that the regulation of glucose and lipid metabolism is not fundamentally impaired in well-controlled insulin-treated diabetic subjects (hemoglobin A 1 [HbA 1], < 10.5%) in the physiological context of meal ingestion, but that coordination of the postabsorptive to postprandial transition does depend on achieving a suitable profile of plasma free-insulin concentrations.

Lack of effect of peripheral nervous blockade on nocturnal fluctuations in lower-leg subcutaneous blood flow in man

1. The local subcutaneous adipose tissue blood flow was measured simultaneously in the right and left lower legs of 10 normal human subjects under out-patient nocturnal conditions. The 133Xe-wash-out technique, portable CdTe(Cl) detectors and a portable data-storage unit were used for the measurement of blood flow. 2. The purpose of the study was to unveil the possible role of centrally controlled nerve fibres to the measurement area as mediators of a previously described nocturnal subcutaneous hyperaemia of 2 h duration. Therefore, before the sleeping period, a local nervous blockade was applied immediately proximal to the isotope depot on the right lower leg by the injection of approximately 15 ml of bupivacaine (5 mg/ml) subcutaneously. 3. Control experiments revealed blockade of the baroreceptor vasoconstrictor reflex activity 4 h after application of the local nervous blockade in three subjects examined. 4. Identical nocturnal isotope-wash-out curves were recorded from the two legs. Subcutaneous blood flow was found to increase significantly (P < 0.0001) after approximately 1 h of sleep and the hyperaemia persisted for 2 h. 5. A significant positive correlation was detected between the latency periods from going to bed until the onset of the hyperaemia in the right and left lower legs (P < 0.001, r = 0.95). 6. No significant difference could be detected between the relative blood flow increase during the hyperaemic phase in the right and left lower legs (P = 0.83). 7. It is concluded that the present data seem to rule out a central nervous factor(s) as the eliciting mechanism of the nocturnal subcutaneous hyperaemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Platelet-activating factor causes hypoketonaemia in starved rats.

1. The aim of this work was to examine whether platelet-activating factor could mimic the hypoketonaemia seen in septic and endotoxic experimental animals. Platelet-activating factor was administered either by the intraperitoneal (high dose) or intravenous (jugular vein, low dose) routes. 2. Intraperitoneal injection of platelet-activating factor (25 micrograms/kg body weight) decreased the blood ketone body concentration (acetoacetate plus 3-hydroxybutyrate) transiently (30 min after injection) in starved rats. Continuous intravenous infusion of platelet-activating factor (40 ng min-1 kg-1 for 5 h) caused comparable hypoketonaemia. 3. The hepatic acetoacetate concentration also decreased transiently after injection of platelet-activating factor and there was an increase in the 3-hydroxybutyrate/acetoacetate ratio. The hepatic ATP concentration decreased at 15 and 30 min after injection of platelet-activating factor. Infusion of platelet-activating factor caused a similar decrease in hepatic ketone body concentration, but no significant change in the 3-hydroxybutyrate/acetoacetate ratio or adenine nucleotide concentrations. 4. Platelet-activating factor administered by infusion, but not by injection, decreased the plasma non-esterified fatty acid concentration. The plasma glycerol concentration also decreased after infusion of platelet-activating factor, suggesting decreased lipolysis in adipose tissue. 5. Changes in plasma insulin concentration or white adipose tissue blood flow did not appear to contribute to the decrease in the plasma non-esterified fatty acid concentration after infusion of platelet-activating factor. However, there was a significant decrease in blood flow to interscapular brown adipose tissue in both the infused and injected groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Nocturnal variations in human lower leg subcutaneous blood flow related to sleep stages.

Nocturnal subcutaneous adipose tissue blood flow rate was measured in the lower legs of 10 normal human subjects together with systemic arterial blood pressure, heart rate, and registration of sleep stages under ambulatory conditions. The 133Xe washout technique, portable CdTe(Cl) detectors, and a portable data storage unit were used for measurement of blood flow rates. The sleep recordings were performed with a portable computerized sleep analysis system. In accordance with the results of previous studies, a hyperemic blood flow rate phase (mean increase 140%) for 100 min was observed approximately 60 min after the subjects went to bed. The moment of onset of the hyperemic phase was closely related to the moment of onset of the first episode of deep sleep (stages 3 and 4). There was a significant (P < 0.01) overrepresentation of deep sleep in the hyperemic phase compared with adjacent phases, and rapid-eye-movement sleep predominantly occurred in the latter part of the night, when the subcutaneous blood flow rate was stable. The results of the present study are in accordance with current theories of the interrelationship between the thermoregulatory and the arousal state control systems and, thus, might suggest that the nightly subcutaneous hyperemia represents a thermoregulatory effector mechanism.

Glycerol production in subcutaneous adipose tissue in lean and obese humans.

To estimate the regional subcutaneous glycerol production rate in normal and obese humans, the venous arterialized plasma glycerol, interstitial glycerol in the subcutaneous adipose tissue together with adipose tissue blood flow (ATBF, ml/100 g.min) were measured in the postabsorptive state and for 2 h after ingestion of 100 g of oral glucose. Eight lean and eight obese men with normal oral glucose tolerance tests were investigated with the subcutaneous microdialysis technique and 133Xe clearance. In the postabsorptive state, the interstitial glycerol concentrations in lean and obese subjects were 170 +/- 21 vs. 282 +/- 28 microM (P less than 0.01) and 156 +/- 23 vs. 225 +/- 12 microM (P less than 0.05) in the abdominal and femoral subcutaneous adipose tissue, respectively. The corresponding arterial glycerol levels were 54 +/- 4 vs. 75 +/- 14 microM (NS). Abdominal ATBF was greater in lean subjects (3.2 +/- 0.6 vs. 1.6 +/- 0.3; P less than 0.05), whereas femoral ATBF was similar in both groups (2.7 +/- 0.4 vs. 2.4 +/- 0.7). Estimated mean local glycerol release (mumol/100 g.min) was similar in the lean and obese group (0.16 +/- 0.03 vs. 0.20 +/- 0.05 and 0.18 +/- 0.02 vs. 0.17 +/- 0.04) in the abdominal and femoral site, respectively. We conclude that glycerol production from the subcutaneous tissue is increased in obesity, irrespective of adipose tissue distribution. This enhancement is due to the increased adipose tissue mass.

Subdermal penetration of topically applied clobetasol propionate in ointment base through intact human skin: Lack of effect on subcutaneous adipose tissue blood flow

Some data have demonstrated a substantial subdermal accumulation of topically applied drugs in animals. The aim of this study was to evaluate a possible effect of epicutaneously applied clobetasol propionate on blood flow in human subcutaneous adipose tissue. Nine healthy subjects were studied. The 133Xenon wash-out method was used for the measurement of subcutaneous blood flow. Resting blood flow and the local blood flow regulatory mechanisms, autoregulation of blood flow and the veno-arteriolar reflex, were assessed prior to treatment and were measured following 24, 48 and 72 h of treatment. The results demonstrated no effect of clobetasol propionate on resting subcutaneous blood flow or the local regulatory mechanisms.

Beta-3 adrenergic agonist, BRL-26830A, and alpha/beta blocker, arotinolol, markedly increase regional blood flow in the brown adipose tissue in anesthetized rats.

Regional vascular effects of some adrenergic agents, focussing on brown adipose tissue (BAT), were investigated using tracer microspheres with a reference sample method in the anesthetized rat. Intravenous injections of 0.5 mg/kg BRL-26830A, a beta 3-adrenergic agonist, increased heart rate, but changes in blood pressure and cardiac output were not significant. The drug decreased blood flow in the brain, the spleen and the kidneys, but markedly increased it in BAT. At 2 mg/kg, arotinolol, an alpha/beta-adrenergic blocker, decreased blood pressure by 20 mmHg and increased cardiac output by 95 ml/min/kg. It slightly but significantly decreased blood flow in the liver and the spleen, but markedly increased the flow in BAT. Acebutolol, a beta 1-adrenergic blocker, decreased blood flow in the liver, the spleen, the pancreas, the kidneys, the adrenals, the skeletal muscle and the skin. Bunazosin, an alpha 1-adrenergic blocker, decreased it in all organs and tissue expect the brain and BAT. The pattern of redistribution of blood flow by arotinolol was very similar to that caused by BRL-26830A. Acebutolol and bunazosin rather decreased the blood flow in the BAT. These results indicate that stimulation of beta 3-adrenergic receptors, in BAT results in vasodilation, and that arotinolol may bind to those beta 3-adrenergic receptors.

Nocturnal variations in lower-leg subcutaneous blood flow in paraplegic men.

1. Lower-leg subcutaneous adipose tissue blood flow rates were measured over 12-20 h under ambulatory conditions by means of the 133Xe-washout technique in nine paraplegic men, all with complete spinal cord lesions at or below the Th 6 level, and in nine age-matched healthy men. Portable CdTe(Cl) detectors and data-storage units were used. 2. The central and local sympathetic vasoconstrictive activity at the lower leg was measured under laboratory conditions by means of the 133Xe-washout technique and a stationary NaI(Tl) detector system. 3. The paraplegic men were found to have intact central and local sympathetic vasoconstrictive activity in their lower legs. Moreover, they all had a nocturnal hyperaemic blood flow phase of the same magnitude and duration as the control subjects. 4. The possibility that the somaesthetic nerves play a role in the hyperaemic response could be excluded, as all the paraplegic men suffered from complete lower-leg somaesthetic denervation. 5. A significant correlation was found between the time of going to bed and the nightly hyperaemic response in the right and left lower legs (P less than 0.01). 6. It is concluded that the present data are in accordance with the concept of a central nervous or humoral elicitation of nocturnal hyperaemia, although local metabolic and other factors might participate as well. Paraplegic men have an intact regulation of the postural and nocturnal changes in peripheral blood flow whether of central sympathetic or humoral origin.

Insulin Absorption, Glucose Homeostasis, and Lipolysis in IDDM During Mental Stress

To study the effects of mental stress on the absorption kinetics of insulin and on glucose homeostasis and lipolysis in insulin-dependent diabetes mellitus (IDDM). Nine IDDM patients were exposed to the Stroop color word conflict test (CWT) during 40 min after injection of 125I-labeled soluble human insulin (10 U) into the abdomen. Adipose tissue blood flow (133Xe-clearance) was determined concomitantly to elucidate the importance of blood flow for insulin absorption during CWT. The effect of the CWT was followed by measurement of arterial levels of catecholamines and as blood pressure and heart-rate responses. Lipolysis was measured as arterial glycerol levels, and ketone body levels were monitored by determination by beta-hydroxybutyrate. Although insulin absorption (residual 125I-radioactivity and plasma free insulin levels) and the arterial levels of glucose and beta-hydroxybutyrate were not significantly changed by the CWT, arterial glycerol and norepinephrine levels and adipose tissue blood flow were approximately doubled, and epinephrine levels increased fourfold. Heart rate increased approximately 35 beats/min and mean blood pressure approximately 25 mmHg. The results suggest that intense mental stress of 40 min duration does not alter the absorption of subcutaneously injected insulin, glucose homeostasis, or ketone body levels in patients with IDDM, despite a considerable increase in blood flow and lipolysis.

Regional variations in nocturnal fluctuations in subcutaneous blood flow rate in the lower leg of man

The purpose of the study was to investigate possible regional variations in recently discovered nocturnal fluctuations in subcutaneous blood flow rates. Approximately 90 min after going to sleep, a 100% blood flow rate increment, lasting about 100 min, has been demonstrated in the distal and medial aspect of the right lower leg of normal human subjects. In the present study subcutaneous adipose tissue blood flow rates were measured simultaneously in the right and left lower legs of 16 normal human subjects over 12-20 h ambulatory conditions. The 133Xe wash-out technique, portable CdTe(Cl) detectors and a portable data storage unit were used. The tracer depots were applied on the medial aspects of the right lower leg and on the medial (series 1) and lateral (series 2) aspect of the left lower leg 10 cm proximal to the malleolar level by means of the epicutaneous, atraumatic labelling technique. A nocturnal hyperaemic response was demonstrated at both the medial and lateral aspect of the leg. As for the degree of hyperaemia and the absolute blood flow rates in the different phases, there were some deviations between the medial and the lateral locations. However, a highly significant positive correlation was observed in both series concerning the duration of the period from going to bed until the hyperaemia phase (P less than 0.001). The mechanisms involved in the nightly subcutaneous hyperaemia are at present unknown. The sudden, synchronized increase in nocturnal subcutaneous blood flow points to a central nervous or humoral elicitation, although local metabolic factors might participate as well.

Nocturnal variations in peripheral blood flow, systemic blood pressure, and heart rate in humans

Subcutaneous adipose tissue blood flow rate, together with systemic arterial blood pressure and heart rate under ambulatory conditions, was measured in the lower legs of 15 normal human subjects for 12-20 h. The 133Xe-washout technique, portable CdTe(Cl) detectors, and a portable data storage unit were used for measurement of blood flow rates. An automatic portable blood pressure recorder and processor unit was used for measurement of systolic blood pressure, diastolic blood pressure, and heart rate every 15 min. The change from upright to supine position at the beginning of the night period was associated with a 30-40% increase in blood flow rate and a highly significant decrease in mean arterial blood pressure and heart rate (P less than 0.001 for all). Approximately 100 min after the subjects went to sleep an additional blood flow rate increment (mean 56%) and a simultaneous significant decrease in mean arterial blood pressure (P less than 0.001) were observed. The duration of this hyperemic phase was 116 min. A highly significant reduction of the subcutaneous vascular resistance (50%) was demonstrated during the hyperemic blood flow rate phase compared with the surrounding phases (P less than 0.0001). The synchronism of the nocturnal subcutaneous hyperemia and the decrease in systemic mean arterial blood pressure point to a common, possibly central nervous or humoral, eliciting mechanism.

Amino acid metabolism in human subcutaneous adipose tissue in vivo

1. Arteriovenous differences for alanine, glutamate and glutamine were measured across subcutaneous adipose tissue and forearm muscle in normal subjects. 2. After an overnight fast, adipose tissue showed net production of alanine and glutamine and uptake of glutamate in each of 11 subjects. 3. In seven subjects, adipose tissue blood flow was measured and the measurements were continued for 6 h after eating a mixed meal. The pattern of amino acid metabolism across the adipose tissue was remarkably little disturbed after the meal, except for a short period of apparent uptake of alanine as the concentration of that amino acid rose. 4. The pattern of amino acid metabolism across adipose tissue was qualitatively similar to that across the forearm, although it differed quantitatively in that glutamate uptake was more prominent (compared with glutamine release) in the adipose tissue. 5. The rates of alanine and glutamine release observed suggest that adipose tissue may play a substantial role in the whole-body production of these amino acids.

Lower leg subcutaneous blood flow during walking and passive dependency in chronic venous insufficiency

The blood flow in the subcutaneous adipose tissue of the lower leg of eight normal subjects and 19 patients with chronic venous insufficiency was measured. The 133Xe-washout technique was used with portable CdT1(C1) detectors and a data storage unit. Only those patients with ulcers and a systolic blood pressure at the toe of greater than or equal to 60 mm were investigated. In the controls the relative blood flow during sitting was 0.61 (range 0.35-0.80). In the patients it was 0.46 (range 0.22-0.87). This difference was not significant. During walking the blood flow increased in controls as well as in the patients compared to the value determined in the sitting position (P = 0.0078 and P = 0.0028, respectively, Wilcoxon matched-pairs test). The relative blood-flow rate during walking was 0.96 (range 0.60-1.58) in the controls, and 1.04 (range 0.49-1.46) in the patients. The difference between the normal subjects and the patients was not significant (P = 0.79). We conclude from our studies that patients with venous insufficiency are able to increase their blood flow during walking to the same extent as normal controls.

Nocturnal variations in subcutaneous blood flow rate in lower leg of normal human subjects

Subcutaneous adipose tissue blood flow rate was measured in the lower leg of 22 normal human subjects over 12- to 20-h ambulatory conditions. The 133Xe washout technique, portable CdTe(Cl) detectors, and a portable data storage unit were used. The tracer depot was applied on the medial aspect of the right lower leg 10 cm proximal to the malleolar level by means of the epicutaneous, atraumatic labeling technique. The change from upright to supine position from day 1 in the beginning of the night period elicited an instantaneous blood flow rate increment of 30-40% in accordance with a decrease in central and local postural sympathetic vasoconstrictor activity. During sleep, characteristic variations in subcutaneous blood flow were disclosed. The 133Xe washout curve could be divided into three segments with significantly different slopes. Approximately 90 min after the subject went to sleep, an additional blood flow rate increment of considerable magnitude was observed. The mean increase was 84%, but in several cases a greater than 200% increment was measured (maximum 244%). The intra-individual coefficient of variation for the nocturnal blood flow response was in triplicate measurements 25% (n = 9). The hyperemic phase lasted approximately 100 min after which the blood flow rate returned to the level measured at the beginning of the night period. The blood flow rates measured on the second day did not differ from those on the first day. Control measurements performed under similar thermal conditions, but with the subjects kept awake, did not reveal any hyperemic phases. This points toward changes in cardiovascular regulatory mechanisms during sleep.(ABSTRACT TRUNCATED AT 250 WORDS)

Increased subcutaneous adipose tissue blood flow in UVB-inflamed human skin. The existence of a cutaneous-subcutaneous reflex mechanism?

No abstract available.